Certain biological chemical compounds such as nerve growth factors (NGF), neurotrophins, brain-derived neurotrophic factors (BDNF), fibroblastic growth factor (FGF), glial cell line-derived neurotrophic factors (GDNF), and numerous other similar biological chemical compounds, all collectively known as survival-type factors can slow down the process of cellular degeneration in a number of biological degenerative diseases, specifically in retinal degenerative diseases and also promote cellular growth in other situations.
In studies, the application of survival-type factors was found to promote and maintain certain retinal cellular functions. For example, brain-derived neurotrophic factor (BDNF), neurotrophin-4 (NT-4), neurotrophin-5 (NT-5), fibroblastic growth factor (FGF) and glial cell line-derived neurotrophic factor (GDNF) have been shown to enhanced neurite outgrowth of retinal ganglion cells and to increase their survival in cell culture. GDNF has been shown to preserve rod photoreceptors in the rd/rd mouse, an animal model of retinal degeneration. Nerve growth factor (NGF) injected into the intra-ocular area of the C3H mouse, also a model of retinal degeneration, results in a significant increase of surviving photoreceptor cells compared to controls (Bosco and Linden, 1999; Caleo et al., 1999; Carmignoto et al., 1989; Cui et al., 1998; Frasson et al., 1999; Lambiase and Aloe, 1996; Reh et al., 1996).
However, while many prostheses are known that attempt to restore vision by using photoactive properties of semiconductors designed to provide sufficient electrical stimulation of retinal cells to induce a perceptual response, few devices or treatments are available that can slow, stop or reverse retinal degeneration.